Enantioselective Generation of 3-Amino-1-oxy-Substituted Carbanions by Sparteine-Induced Deprotonation: Asymmetric Synthesis of 3-Hydroxyalkylamines

Abstract

The O-3-dibenzylamino)propyl carbamate 3a is deprotonated by sec-butyllithium/(-)-sparteine with a high degree of selection between the enantiotopic methylene protons. After quenching the configurationally stable carbanionic intermediate 4a stereospecifically by electrophiles, γ-aminoalkanols 6 are obtained with ≥ 95% ee. The reaction of the dimethylamino derivative 3b under these conditions leads to essentially racemic products which presumably is caused by the competing internal complexation of the lithium cation.